With the development of outdoor locating, indoor locating is currently subjected to a wide concern, becoming an increasingly popular research field. Indoor locating mainly refers to the locating of indoor human or objects and provides some services based on locating such as private service, automatic robot control, mobile business, tracking service and navigation assistance. Until now, many researches based on locating have been proposed, and some techniques and products have used for indoor locating, for example radio frequency signal, wireless local area net (Wi-Fi), infrared, laser, ultrasound etc. Generally speaking, radio frequency signal is the main way of indoor locating, but accuracy of the wireless locating can only limit to meter level. Wi-Fi locating system has also been studied, but the results are all acquired by experiments. These locating techniques have limitations including, for example, low accuracy, existence of electromagnetic interference, requirement of additional equipment and low security etc.
To overcome these drawbacks, locating system based on visible light system (VLC) is widely spread. LED has a longer service circle, a high tolerance against humidity, low power consumption and a friendly relation with environment etc. And, LED lamp can modulate an electrical signal into an optical wave signal for transmitting at a very high speed. Based on these properties, in visible light communication system, LED lamp can not only be an illuminating equipment but also be a communication device. Many different locating algorithms, mainly geometrical methods, have been proposed in existing researches. Geometrical methods include two types: trilateral locating and triangle locating. Trilateral locating achieves locating by distance from multiple receiving points to the target. And the distance from receiving points to the target is mainly acquired by measuring received signal strength (RSS), time of arrival (TOA) and time difference of arrival (TDOA). Trilateral locating achieves locating by angle between multiple receiving points and the target. These locating methods generally have only one receiving device, i.e. the targeted object, whereas the conventional locating schema needs to exhaust and traversal resulting in a complicatedly calculating system.